Encyclopedia of

Fibrin sealants

Definition

Fibrin sealants are a type of surgical tissue adhesive derived from human
and animal blood products. The ingredients in these sealants interact
during application to form a stable clot composed of a blood protein
called fibrin. Fibrin sealants are also called fibrin glues. They have
been used in Japan and Western Europe since the 1980s, but were not
approved for use in the United States until 1998 due to the Food and Drug
Administration's (FDA) concerns about virus contamination. As of
2003, all fibrin sealants used in the United States are made from blood
plasma taken from carefully screened donors and rigorously tested to
eliminate hepatitis viruses, HIV-1, and parvovirus.

Purpose

Originally developed during World War II to stop bleeding from battle
injuries, fibrin sealants are presently used during surgery for several
different purposes:

to control bleeding in the area where the surgeon is operating

to speed wound healing

to seal off hollow body organs or cover holes made by standard sutures

to provide slow-release delivery of medications to tissues exposed
during surgery

Fibrin sealants have several advantages over older methods of hemostasis
(stopping bleeding). They speed up the formation of a stable clot; they
can be applied to
very small blood vessels and to areas that are difficult to reach with
conventional sutures; they reduce the amount of blood lost during surgery;
they lower the risk of postoperative inflammation or infection; and they
are conveniently absorbed by the body during the healing process. They are
particularly useful for minimally invasive procedures and for treating
patients with blood clotting disorders. Fibrin sealants are, however,
being replaced for some specialized purposes by newer wound adhesives
known as cyanoacrylates.

Description

All fibrin sealants in use as of 2003 have two major ingredients, purified
fibrinogen (a protein) and purified thrombin (an enzyme) derived from
human or bovine (cattle) blood. Many sealants have two additional
ingredients, human blood factor XIII and a substance called aprotinin,
which is derived from cows' lungs. Factor XIII is a compound that
strengthens blood clots by forming cross-links between strands of fibrin.
Aprotinin is a protein that inhibits the enzymes that break down blood
clots.

Preparation

The preparation and application of fibrin sealants are somewhat
complicated. The thrombin and fibrinogen are freeze-dried and packaged in
vials that must be warmed before use. The two ingredients are then
dissolved in separate amounts of water. Next, the thrombin and fibrinogen
solutions are loaded into a double-barreled syringe that allows them to
mix and combine as they are sprayed on the incision. Pieces of surgical
gauze or fleece may be moistened with the sealant solutions to cover large
incisions or stop heavy bleeding.

As the thrombin and fibrinogen solutions combine, a clot develops in the
same way that it would form during normal blood clotting through a series
of chemical reactions known as the coagulation cascade. At the end of the
cascade, the thrombin breaks up the fibrinogen molecules into smaller
segments of a second blood protein called fibrin. The fibrin molecules
arrange themselves into strands that are then cross-linked by a blood
factor known as Factor XIII to form a lattice or net-like pattern that
stabilizes the clot.

Fibrin sealants are undergoing rapid refinement as the result of recent
advances in tissue adhesives in general. In 1997, the Tissue Adhesive
Center was founded at the University of Virginia Health Sciences Center in
order to develop and test new fibrin sealants and other surgical glues.
Recent developments include a delivery system that forms a fibrin sealant
from the patient's own blood within a 30-minute cycle, and uses a
spraypen rather than a double-barreled syringe for applying the sealant.
The use of the patient's own blood lowers the risk of allergic
reactions to blood products derived from animal or donated blood.

Normal results

Reports that have been published between 2001 and 2003 indicate that
fibrin sealants are a safe and highly effective form of surgical adhesive.
A survey done in 2000 at the University of Virginia hospital found that
over 90% of the surgeons who had tried fibrin sealants were pleased with
the results. Several American studies have reported that fibrin sealants
have improved surgical outcomes significantly by shortening the time
required for operations; lowering the rate of infections and other
complications; minimizing blood loss during surgery; and reducing the
amount of scar tissue formed over incisions. German researchers have found
that fibrin sealants containing Factor XIII generally give better results
than those that do not.